There is a widely employed arrangement of automobile clutch devices in which: a pressure plate rotating integrally with a flywheel is pressed via a diaphragm spring toward the flywheel to thereby sandwich clutch plates rotating integrally with an input shaft of a transmission between the flywheel and the pressure plate and transfer a rotating force of an engine to the transmission; and the pressure plate is released from the pressing operation of the diaphragm spring to thereby let clutch plates run idle between the flywheel and the pressure plate and sever the transfer of rotating force from the engine to the transmission.
A widely used universal clutch device for general automobiles has cushion plates interposed between clutch plates for smooth clutch operations, thereby making the depression range of a clutch pedal wider to obtain a half-clutch state. For racing cars, however, a clutch is configured so as to achieve shift transmission in a short time and no cushion plates are provided to minimize inertial weights of clutch plates and lighten a load on the transmission as much as possible. This makes the depression range of a clutch pedal narrow to obtain a half-clutch state (hereinafter, referred to as simply half-clutch range). Accordingly, there is a problem that the clutch is engaged more quickly than expected, thereby bringing about a shock.
To prevent generation of such a shock, there has been proposed a clutch device with a wider half-clutch range in which a cushion ring is provided between the pressure plate and the diaphragm spring; the plane of the pressure plate facing the cushion ring is formed in a tapered shape; a gap is created between the pressure plate and the inner periphery of the cushion ring; and the gap is used to deform the cushion ring elastically toward the pressure plate (refer to Patent Document 1, for example).
[Patent Document 1] JP-A No. 9-250556